Flow governors currently in use appear by-and-large either in the form of a valvecock forced onto a seat by means of a cam or similar part operated by a flexible diaphragm distorting under the pressure of the gas, or as a piston valve controlling a series of ring-type joints closing off more-or-less a number of ports, or else as a rotary box, or finally as a conical-tipped needle pressed onto a seat of equivalent shape.
The use of a conical needle has drawbacks with respect to the known designs. Hitherto, the conical tip of the needle has been made of a flexible substance allowing a certain amount of distortion in order to meld to all the defects of configuration possibly present in the seat intended to cooperate with it. Said flexible substance was frequently India rubber or some analogous synthetic material. Use of such substances is barred in connection with use with carbonic acid gas which, on reacting with these materials, makes them porous. Furthermore the production of a metal valve requires fine precision in machining since the slightest error in parallax renders the closing of the controlled piping ineffective.